This invention relates to a pharmaceutical composition for suppository containing N-cyclopropylmethyl-7.alpha.-[(S)-1-hydroxy-1,2,2-trimethylpropyl]-6,14-en do-ethano-6,7,8,14-tetrahydronororipavine (hereinafter referred to as buprenorphine) which is useful as a potent analgesic, or its pharmaceutically acceptable acid addition salt as an active ingredient, having excellent absorption and low irritation.
Buprenorphine is a known compound, and it is, for example, listed on page 207 of The Merck Index (10th Edition), and has been proved by clinical studies to be a potent antagonistic analgesic free from psychotomimetic action which is generally found in narcotic antagonistic analgesics.
Conventionally, buprenorphine is widely used as a parenteral injection for postoperative pain, cancerous pain, anesthesia aid, pain caused by myocardial infraction and others. But the injection is not preferable for patients being treated for a long period, for example, in the cases of intractable chronic pain such as cancerous pain, because frequent administrations are needed, considerable pain accompanies injection, and treatment at home is not possible.
On the other hand, when buprenorphine is orally administered, it is metabolized quickly in the body, and a satisfactory analgesic effect is not expected in its oral dosage form. With this background, the development of buprenorphine suppository has been keenly desired.
However, when buprenorphine is prepared into a suppository form using an oleaginous base which is an ordinary suppository vehicle, the active ingredient cannot be absorbed sufficiently, or when a water-soluble base, (for example, polyethylene glycol) another ordinary suppository vehicle, is used, the absorption rate is low and the rectal mucosa is irritated, and because of these demerits, useful suppositories have not been obtained. Thus, so far, successful intrarectal administration of buprenorphine has not been known.